Closed cell polyolefin foams are commercially produced and used in various applications including automotive, furniture, gasketing, sealing and adhesives.
In these applications, a foam that is soft is often desirable. For example, in the case of an automotive door panel upper, a firm foam will not compress when an elbow is casually placed upon it. Hence, such a foam does not serve its primary purpose of providing a comfortable cushion for the elbow as it rests upon the panel. As a gasket for an electronic component, a firm foam will “push back” against a sensitive or flexible component and will consequently warp or damage that component.
A foam with good haptics is also desirable. Good haptics result in a pleasant soft touch “plush” or “rich” feel to the foam. It is especially desirable in any situation where the foam is being used to impart a feeling of comfort and softness to anyone contacting the foam. Good haptics result in a desirable soft touch feel that is measured by a lack of initial resistance to the gradual compressive displacement of a foam. We quantify such a desirable soft touch feel of a foam with a “haptic factor” which is described below. Intuitively, one would assume that the softer the foam, then the more of a soft touch feel the foam should have. However, foams that are equally soft are not necessarily haptically equivalent. Hence, the need to discuss “softness” and “haptics” as separate characteristics.
Additionally, thermally stable foams are needed in situations where a foam may become heated. Examples of such situations include heat laminating a skin or fabric to a foam; vacuum forming a foam laminate to a substrate; compression molding a foam laminate to a substrate; and end uses where the foam is exposed to constant or intermittent elevated temperatures. Importantly, thermally stable foams are suitable for more commercial applications and markets.
The moldability of a foam is critical in thermoforming processes such as vacuum, pressbond, compression, low pressure and other molding processes. During these molding processes, foams will elongate and bend under tension and the shear forces placed on the foam. The more the foam can elongate and withstand shear forces placed upon it when forming, the better its moldability. With increasing moldability, the foam will be capable of forming more complex shapes and deeper draws before ultimately tearing. Product designers and manufacturers desire foams with better moldability to allow them to create and produce part designs of ever increasing complexity and deeper draws. Importantly, a foam with better moldability can be lighter and still maintain functionality.
Additionally, foams with exceptional “shear strength” as described below are needed. Such foams are useful as mounting tapes where exceptional softness is necessary to ensure sufficient contact with irregular surfaces to be joined and where exceptional shear strength is also necessary. Foam with exceptional shear strength at elevated temperatures is also important in injection molding or low pressure injection molding applications.
Thus, a need exists for crosslinked olefin foams which solve the problem of sacrificing one of these five desired foam physical properties for another. Furthermore, there is a need for methods of making such foams.